private void button1_Click(object sender, EventArgs e)
        {
            ChangeAvatar form   = new ChangeAvatar();
            DialogResult result = form.ShowDialog();

            if (result == DialogResult.OK)
            {
                pictureBox1.Image = form.selectedImage;
                image             = form.selectedImage;
            }
        }
        private void button1_Click(object sender, EventArgs e)
        {
            User user = (User)listBox1.SelectedItem;

            if (user != null)
            {
                ChangeAvatar avatarForm = new ChangeAvatar();
                DialogResult result     = avatarForm.ShowDialog();
                if (result == DialogResult.OK)
                {
                    user.avatar       = avatarForm.selectedImage;
                    pictureBox1.Image = user.avatar;
                }
            }
        }